The present invention relates to disposable hygiene products and more specifically, to methods and apparatuses for processing disposable hygiene products such as baby diapers, adult diapers, disposable undergarments, incontinence devices, sanitary napkins and the like.
More specifically, the invention relates to novel vacuum commutation. A puck or drum is used in a novel way with a novel vacuum applicator. Vacuum, which for the purpose of the following description is defined to mean air pressure that is lower than ambient air pressure, is used in many parts of a diaper manufacturing process. For instance, during pulp core formation, ambient air flows through the surface of the forming pockets to the vacuum manifolds. This airflow pulls pulp fibers into forming pockets on a core forming drum. Elsewhere along the manufacturing process, vacuum is used. For instance, a common method of applying discrete pieces of one web to another is by use of a slip-and-cut applicator. A slip-and-cut applicator is typically comprised of a cylindrical rotating vacuum anvil, a rotating knife roll, and a transfer device. In typical applications, an incoming web is fed at a relatively low speed along the vacuum face of the rotating anvil, which is moving at a relatively higher surface speed and upon which the incoming web is allowed to “slip”. A knife-edge, mounted on the rotating knife roll, cuts a off a segment of the incoming web against the anvil face. This knife-edge is preferably moving at a surface velocity similar to that of the anvil's surface. Once cut, the web segment is held by the air pressure differential between the ambient air on the exterior of the web segment and the vacuum holes on the anvil's face as it is carried at the anvil's speed downstream to the transfer point where the web segment is transferred to the traveling web. Vacuum can also be used in vacuum conveyors.
Typical vacuum rolls used in the prior art have rows of vacuum holes which are fed by cross-drilled ports, each being exposed to the source of vacuum by commutations, as the ports move into a zone of negative pressure in a stationary manifold. Such a configuration serves to apply vacuum sequentially to each successive row of holes.
Continual improvements and competitive pressures have incrementally increased the operational speeds of disposable diaper converters. As speeds increased, the mechanical integrity and operational capabilities of the applicators had to be improved accordingly. The prior art is quite successful when processing nonporous or low porosity full-width or symmetrical webs using vacuum, and vacuum is nearly universally used in diaper production. However, as speeds have increased in manufacturing and raw material webs have become more porous and lighter weight, so too has vacuum demand increased. Along with significant increase in vacuum demand comes the expense of powering conventional vacuum forming techniques, and the noise associated with traditional vacuum pumps.
It is therefore an object of this invention to provide an apparatus which can provide a better solution for vacuum commutation. The vacuum can be used for whatever purpose desired, including maintaining control over diaper webs or discrete portions of diaper webs, including sections of various shapes, and to decrease reliance on traditional vacuum generation.